The abilities of malignant tumor cells to invade adjacent tissues and spread via the blood to implant, invade and form secondary tumor metastases at distant host sites are determined, in part, by cell-cell interactions. Animal model systems have been developed to study such phenomena, such as the series of variant murine B16 melanoma sublines selected in vivo enhanced organ colonization properties, or in vitro for enhanced tissue invasion and other characteristics. However, there are few studies on the determinants of human metastatic cells which are involved in metastasis to distant sites. We will utilize the human A375 melanoma parental cell lines and sublines and clones that possess different metastatic potentials and other characteristics in athymic nude mice. In addition, we will also examine the properties of melanoma cells obtained from patients with malignant melanomas at primary and secondary sites. The biochemical properties to be examined for their role in metastasis of human malignant melanoma are: cell surface glycoproteins, enzymes and other components that may be involved in cell-cell interactions, such as invasion and other metastatic properties. We have recently shown that the display of specific cell surface molecules correlates with the ability of murine melanoma cells to colonize distant sites, such as lung, brain and ovary. In addition, we have recently shown that two enzymes (collagenase IV and heparanase) correlate with metastatic properties. Cell surface glycoprotein will be examined on human malignant melanoma cells, and one of the metastasis-associated enzymes (heparanase) will be purified and characterized. Adhesive and invasive properties of the A375 melanoma cells will be determined using target and non-target-derived human endothelial cells, subendothelial matrix, and organ-derived animal tissues. We have recently established human endothelial cell strains from brain and lung microvasculature. These cells will be characterized and used in cell-cell interactions studies with various human malignant melanoma cells.